Yes. Always interpret "best practice" as "what you won't get fired for doing".

I've signed many contracts with this clause. I've always interpreted it as "if you post what you did on HN and everyone responds saying you clearly shouldn't have done that", then it isn't best practice.

I don't know. For a start, a working bureaucracy would tell you that you must use the term “recommended practices” instead.

I mean, it’s not like we’ve ever seen this with the agile movement /s.

I’ve gone through “agile transitions” in government contracting, at a high level it starts out with a high concept idea of reducing lead times and increasing productivity. Then directives get handed down through layers of management, the decision is made to adopt Scrum or SAFe™, that gets handed down to middle management, who tailor the process in ways that specifically benefit themselves, and you end up with waterfall done poorly and with extra steps™.

What will happen is that there will be very loose definitions of source code and flexible definitions timing when code is released. If an agency does not want to share, they’ll find a way to evade, and still check off the box.

Sure, but won't there also be some agencies who voluntarily implement sharing in the spirit of the law? And won't that be positive for them and their dept's reputation?